1. Field of the Invention
The invention relates to medical methods and devices and, more particularly, to methods and devices for accessing the chambers of the heart through a minimally invasive myocardial puncture.
2. Description of the Related Art
Considerable effort and money is being directed toward replacement of diseased or damaged cardiac valves through minimally invasive techniques. Current approaches for aortic valve replacement include trans-catheter access from an iliac or femoral artery catheter insertion point. Another procedure being explored is transapical valve replacement. The procedure for transapical aortic valve replacement involves surgically accessing the heart through the fourth or fifth intercostal space, dividing the pericardium to expose the heart, making an incision in the heart, dilating the incision, and performing the valve replacement procedure through the dilated incision in the apex of the ventricular myocardium, while the heart continues to beat and function.
Transapical aortic valve implantation (TA-AVI) is being evaluated in patients suffering symptomatic aortic stenosis and an increase perioperative risk. Transapical access is based on clinical experience with de-airing the heart, through the tip (apex) of the left ventricle, during routine cardiac surgical interventions. Insertion of a catheter, and follow-on closure, through the apex is possible in a relatively uncomplicated manner. An anterolateral mini-thoracotomy provides a relatively simple and standardized access to the apex of the heart. This procedure is applicable in almost all patients and they can be extubated soon afterwards. The mini-thoracotomy procedure can be performed without intubation under regional anesthesia in some patients.
From the apex of the left ventricle, the aortic valve can be readily accessed. The major advantage of transapical access is a direct, and antegrade, approach to the aortic valve. By virtue of short distances and direct access, precise positioning of an aortic valve prosthesis inside the stenosed native valve can be executed from the left ventricular apex. An additional benefit of the technique is minimal manipulation in the aortic arch. This is definitively associated with reduced risk of mobilizing intravascular calcifications and thus with a reduced stroke risk. The lower stroke risk of the transapical, in comparison to the trans-femoral, aortic valve implantation technique, has been published in the medical literature.
Transapical aortic valve replacement procedures are performed by a team comprising cardiac surgeons, cardiologists, and anesthetists. High quality imaging, including fluoroscopy, is required and the procedures are performed in the setting of a hybrid operative theatre suitable for both catheterization and open heart cardiothoracic surgery.
TA-AVI can be performed as an off-pump procedure. Femoral guidewires are placed to be able to convert to cardiopulmonary bypass for the safety of the patient in case a bail-out is required. The ventricular apex is reached by means of an anterolateral mini-thoracotomy in the fourth, fifth, or sixth intercostal space. Purse string sutures are placed at the apex. Valve implantation is then performed over guidewires that are inserted, antegrade, under fluoroscopic visualization. The ventricular apex can be closed using the prepositioned purse string sutures after completion of the procedure. The chest is then closed in a routine fashion. The patient can then be extubated and moved to the recovery area.
Suggested further reading related to transapical valve replacement includes: Beyersdorf, F, Transapical Transcatheter Aortic Valve Implantation, Eur J Cardiothoracic Surg, 2007; 31:7-8, and Jian Ye, et al. Six-Month Outcome of Transapical Transcatheter Arotic Valve Implantation in the Initial Seven Humans, European J CardioThorac Surg, 2007; 31:16-21, the entirety of which are incorporated by reference herein
Current access systems are relatively crude and suboptimal for transapical procedures. It would be desirable to have an improved sheath that would maximize access while minimizing myocardial trauma, procedure time, comorbidities, as well as improving healing and patient outcomes.